High-pressure fuel accumulator

ABSTRACT

A high-pressure fuel accumulator for a common-rail fuel injection system of an internal combustion engine has a tubular main body ( 1 ) to which is welded at least one bushing ( 13 ) for connecting a high-pressure line ( 6 ).  
     To improve the quality and safety of the high-pressure connections, a collar ( 14 ) is formed on the end of the bushing ( 13 ) facing the main body ( 1 ).

BACKGROUND INFORMATION

[0001] The present invention relates to a high-pressure fuel accumulatorfor a common-rail fuel injection system of an internal combustionengine, having a tubular main body to which is welded at least onebushing for connecting a high-pressure line.

[0002] A high-pressure fuel accumulator of this kind is described, forexample, in European Patent Application 866,221 A1. In common-railinjection systems a high-pressure pump, possibly with the assistance ofa pre-supply pump, conveys the fuel to be injected from a tank into thecentral high-pressure fuel accumulator, which is known as the commonrail. Fuel lines lead from the rail to the individual injectorsassociated with the cylinders of the internal combustion engine. Theinjectors are controlled individually by the engine electronic system asa function of the operating parameters of the internal combustion engineto inject fuel into the combustion chamber of the internal combustionengine.

[0003] The object of the present invention is to improve the quality andsafety of the high-pressure connections in a high-pressure fuelaccumulator of the type described in the preamble. In addition, thehigh-pressure fuel accumulator according to the present invention shouldhave a simple design and should be inexpensive to manufacture.

[0004] This object is achieved with a high-pressure fuel accumulator fora common-rail fuel injection system of an internal combustion engine,having a tubular main body to which is welded at least one bushing forconnecting a high-pressure line, by the fact that a collar is formed onthe end of the bushing facing the main body.

ADVANTAGES OF THE INVENTION

[0005] The collar is used for introducing the welding current requiredfor welding the bushing. In the case of conventional bushings without acollar, the welding electrode is applied to the end of the bushingfacing away from the main body. In this case, welding splashes can enterthe interior of the bushing and can damage a thread provided there. Inaddition, the geometry in the interior of the bushing may be deformed inan unwanted manner due to the temperatures that occur in welding. Thesedisadvantages are avoided by providing the collar according to thepresent invention as a point of action for a welding electrode. Anotheradvantage is that the collar forms a point of action for a force whichpresses the bushing against the main body during welding. Such a forcecan practically also be applied with the welding electrode.

[0006] A special embodiment of the present invention is characterized inthat a bore leads from the interior of the tubular main body, openinginto a receiving funnel which widens toward the outside and is used toreceive one end of the high-pressure line which is pressed against thereceiving funnel by an essentially hollow cylindrical press-screw sothat it is tight under high pressure, and the seal is surrounded by anessentially hollow cylindrical insulation ring. An electric shunt isreliably prevented by the insulation ring when welding the bushing. Inaddition, the insulation ring prevents welding splashes from reachingthe seal when welding the bushing.

[0007] Another special embodiment of the present invention ischaracterized in that the insulation ring is premounted in the bushing,and the inner lateral surface of the insulation ring is in contact withthe outer lateral surface of a projection in which the receiving funnelis formed. This yields the result that the bushing is centered relativeto the projection in assembly before welding.

[0008] Another special embodiment of the present invention ischaracterized in that the end of the high-pressure line is designed in aball shape, and the inside diameter of the press-screw is larger thanthe outside diameter of the high-pressure line. This permits a clearanceof the high-pressure line relative to the bushing. This yields theadvantage that any installation tolerances in the engine compartment canbe compensated.

[0009] Another special embodiment of the present invention ischaracterized in that the end 5 face of the bushing which faces thetubular main body is tapered toward the inside.

[0010] Due to this tapering, access to the connecting point between thebushing and the tubular main body is facilitated.

[0011] Additional advantages, features and details of the presentinvention are derived from the following description, in which twoembodiments of the present invention are described in detail withreference to the drawing. The features mentioned in the claims and thedescription may be essential to the present invention eitherindividually or in any combination.

DRAWING

[0012] The drawing shows:

[0013]FIG. 1 a view of a cross section through a high-pressure fuelaccumulator according to a first embodiment of the present invention,and

[0014]FIG. 2 a view of a cross section through a high-pressure fuelaccumulator according to a second embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0015] The high-pressure fuel accumulator shown in cross section in FIG.1 includes a tubular main body 1. A longitudinal bore 2 in tubular mainbody 1 is used to store the fuel which is under a high pressure. Aplurality of transverse bores, only one of which is shown in FIG. 1,namely transverse bore 3, lead away from longitudinal bore 2. Transversebore 3 opens outward in a receiving funnel 4. Receiving funnel 4 isdesigned in a conical shape and forms a sealing face for a spherical end5 of a high-pressure line 6. Spherical end 5 of high-pressure line 6develops into an area 7 having a widened outside diameter. A pressureshoulder 8 is formed on the outside of high-pressure line 6 followingarea 7 having a widened outside diameter.

[0016] A depression 9, which is formed on the inner circumference of theend of a press-screw facing tubular main body 1, is in contact withpressure shoulder 8 of high-pressure line 6. Press-screw 10 hasessentially the shape of a hollow circular cylinder through whichhigh-pressure line 6 passes. Press-screw 10 is provided with an outsidethread 11 which interacts with an inside thread 12 formed in a hollowcylindrical bushing 13.

[0017] A collar 14 is provided on bushing 13 on the end facing tubularmain body 1. A taper 15 is formed on the end face of bushing 13 whichfaces tubular main body 1. Taper 15 is approximately perpendicular to adepression 19, which is formed on the inner circumference of bushing 13.At the interface between taper 15 and depression 19 there is aperipheral edge which is rounded and sits on a flattened surface 20which is formed on tubular main body 1. The connection between bushing13 and tubular main body 1 is formed by a weld 16.

[0018] A projection 17 is formed on tubular main body 1 at the center offlattened surface 20. Receiving funnel 4 is arranged at the center ofprojection 17. On the outside, projection 17 has the shape of a cylinderwhich is surrounded by an insulation ring 18. The insulation ring hasthe shape of a hollow circular cylinder which is fitted into bushing 13.

What is claimed is:
 1. A high-pressure fuel accumulator for acommon-rail fuel injection system of an internal combustion engine,having a tubular main body (1) to which is welded at least one bushing(13) for connecting a high-pressure line (6), wherein a collar (14) isformed on the end of the bushing (13) facing the main body (1).
 2. Thehigh-pressure fuel accumulator according to claim 1, wherein a bore (3)leads from the interior (2) of the tubular main body (1), opening into areceiving funnel (4) which widens toward the outside and is used toreceive one end (5) of the high-pressure line (6) which is pressedagainst the receiving funnel (4) by an essentially hollow cylindricalpress-screw (10) so that it is tight under high pressure, and the sealis surrounded by an essentially hollow cylindrical insulation ring (18).3. The high-pressure fuel accumulator according to claim 2, wherein theinsulation ring (18) is premounted in the bushing (13), and the innerlateral surface of the insulation ring (18) is in contact with the outerlateral surface of a projection (17) in which the receiving funnel (4)is formed.
 4. The high-pressure fuel accumulator according to claim 2 or3, wherein the end (5) of the high-pressure line (6) is designed in aball shape, and the inside diameter of the press-screw (10) is largerthan the outside diameter of the high-pressure line (6).
 5. Thehigh-pressure fuel accumulator according to one of the preceding claims,wherein the end face of the bushing (13) which faces the tubular mainbody (1) is tapered toward the inside.